The present invention relates to a method and a device for estimating a current open-circuit voltage characteristic of a battery.
Present-day battery systems are able to determine a current capacity and a current state of health of an associated battery, and to make these available. For this purpose, it is necessary to acquire a time characteristic of a battery voltage and of a battery current of the battery.
A change in the charge level of the battery can be determined from the time characteristic of the battery voltage and an open-circuit voltage characteristic of the battery. A delivered or received charge of the battery, referred to later as a change in charge, can be determined from the time characteristic of the battery current.
A current capacity of the battery can be inferred from the change in charge and from the change in the charge level. The state of health of the battery can be inferred from the current capacity of the battery and an original capacity of the battery.
In this case there arises that problem that, in order for the capacity and the state of health of the battery to be calculated accurately, the change in charge and the associated change in the charge level must be very large in order to obtain precise information. Consequently, for a precise calculation of this information, an almost complete charging and discharging cycle is required.
In addition, there arises the problem that the open-circuit voltage characteristic of the battery is not constant over the service life of the latter, and imprecise capacity calculations may result from an open-circuit voltage characteristic, on which the calculation is based, that is no longer current.
JP2012-137330, the contents of which are incorporated by reference, discloses a method in which an open-circuit voltage characteristic of a battery is determined on the basis of a characteristic curve of an anode potential and of a characteristic curve of the cathode potential.